Jiang Jingxing, Liu Yan, Hou Cheng, Li Yinwu, Luan Zihong, Zhao Cunyuan, Ke Zhuofeng
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
Org Biomol Chem. 2016 Apr 14;14(14):3558-63. doi: 10.1039/c6ob00215c. Epub 2016 Mar 15.
Gold catalyzed rearrangement of propargylic esters can undergo 1,3-acyloxy migration to form allenes, or undergo 1,2-acyloxy migration to access gold-carbenoids. The variation in migration leads to different reactivities and diverse cascade transformations. The effect of terminal substituents is very important for the rearrangement. However, it remains ambiguous how terminal substituents govern the selectivity of the rearrangement. This study presents a theoretical model based on the resonance structure of gold activated propargylic ester complexes to rationalize the rearrangement selectivity. Substrates with a major resonance contributor A prefer 5-exo-dig cyclization (1,2-migration), while those with a major resonance contributor B prefer 6-endo-dig cyclization (1,3-migration). This concise model would be helpful in understanding and tuning the selectivity of the metal catalyzed rearrangement of propargylic esters.
金催化的炔丙基酯重排反应可以经历1,3 - 酰氧基迁移以形成联烯，或者经历1,2 - 酰氧基迁移以生成金卡宾。迁移方式的不同导致了不同的反应活性和多样的串联转化。末端取代基的影响对重排反应非常重要。然而，末端取代基如何控制重排反应的选择性仍不明确。本研究基于金活化的炔丙基酯配合物的共振结构提出了一个理论模型，以合理化重排反应的选择性。具有主要共振贡献体A的底物倾向于5 - 外向 - 环化（1,2 - 迁移），而具有主要共振贡献体B的底物则倾向于6 - 内向 - 环化（1,3 - 迁移）。这个简洁的模型将有助于理解和调控金属催化的炔丙基酯重排反应的选择性。
